Adjustable automatic pipette



April 9, 1946. w D. LONG ADJUSTABLE AUTOMATIC P IPETTE Filed Dec.

FIG.

FIG. 2.

. INVENTOR' WENDAL D.

LO NG ATTQRNEY Patented Apr. 9, 1946 ADJUSTABLE AUTOMATIC PIPETTE WendalD. Long, Los Angeles, Calif., assignor to Horton & Converse, LosAngeles, Oalifi, a corportion of California Application December 11,1942, Serial No. 468,738

3 Claims.

My invention relates to improvements in automatic pipettes of theoverflow type; and the object of my improvement is to provide a methodfor adjusting the volume delivered by the pipette.

I attain this object by mechanism illustrated in the accompanyingdrawing, in which Figure 1 is vertical section of a double actionpipette; Figure 2 a vertical section of a single action pipette; Figure3 a vertical section of the barrel of the volume chamber; and Figure 4 avertical section of the movable plunger and overflow bulb.

Similar numerals refer to similar parts throughout the several views.

Delivery of a desired volume of liquid is accomplished by regulating thevolume of chamber I by adjusting the position of plunger 2 in barrel 3.The plunger is held in place by a suitable clamp.

In operation, with stopcock 6 in fill position, liquid from reservoir 4flows through tube 5 and stopcock 6, fills chamber 1, then rises in tube1, overflows into bulb 8, then flows through tube 9 and rises inflexible tube Hi to the level of liquid in reservoir 4. When stopcock 6is in empty position, liquid flows downward from overflow tip ll, tube land chamber I through stopcock 6, and out delivery tube I2. The liquidin tube 9 and flexible tube It) flows into overflow bulb 8 and on thenext cycle is forced into reservoir 4 at point l3.

An opening it into reservoir 4 is provided to equalize the pressurewithin the apparatus when liquid is delivered.

In operation of double action adjustable automatic pipette Fig. 1, onechamber is filled while the other is emptied by use of a double Ystopcock.

The apparatus is preferably but not necessarily constructed of glasswith the exception of flexible tube H] which is rubber or other suitablematerial. The invention is designed to deliver a multiplicity of volumesof liquid with great accuracy, one of its principal uses being foranalytical procedures. This accuracy is attained by reason of the factthat the liquid delivered is only that portion contained in vent pipe I,chamber I, stopcock 6 and outlet tube [2. The bulb 8 serves theessential function of trapping the overflow liquid (from fillingoperation) contained in tubes 9 and H). The tube in is necessarilyconnected to reservoir 4, as it serves the necessary function ofallowing the liquid trapped in the overflow bulb 8 to be forced outthrough tubes 9 and I0 into the reservoir 4, which enables the air inthe empty system to be replaced by liquid during the filling cycle. Inoperation, liquid from the reservoir 4 flows downward through tube 5into stopcock 6 filling one adjustable chamber I and then flowingupwardly through hollow rod 1 overflowing into overflow bulb 8. Theoverflow liquid then rises in return flow tube ID to the liquid level inthe reservoir. On turning the stopcock 6 one-half turn, the liquid flowsdownward from overflow point I l emptying the adjustable chamber at thedelivery tube l2, the volume delivered being regulated by raising orlowering the plunger 2. The liquid in the return flow tube is trapped inoverflow bulb B and is forced back into the reservoir on the next cycle.One pipette fills as the other one delivers, thus one volume isdelivered with each one-half turn of the stopcock. The air vent I 4serves several purposes. It equalizes the air pressure in the reservoirwhen the unit is being used without connection to a bulb bulk supplysource, may be connected to a bulk supply source arranged to flow intothe reservoir 4 by gravity. and air pressure may be applied through thisvent where greater filling speed is desired or heavy liquids are beinghandled. When one side of the device has discharged, the liquidpreviously in tube II! is trapped in bulb 8. The amount dischargedcannot possibly vary from the volume of the chamber, outlet system andvent pipe 1.

I am aware that prior to my invention automatic pipettes of the overflowtype have been made. However, to my knowledge none have been made withthe adjustable feature herein described.

I therefore claim:

1. A structure of the class described comprising a reservoir, a chamberbelow the same, a conduit depending from the reservoir and communicatingwith the lower portion of said chamber, a piston in said chamber, saidpiston being adjustable in the chamber to vary the capacity of thelatter, a bulb on said piston disposed above said chamber, a hollow rodextending from the piston so that material may pass from the chamberinto the bulb, said hollow rod being disposed within said bulb so as toform a trap, and a tube extending upwardly from said bulb andcommunicating with said reservoir above said conduit.

2. A structure of the class described comprising a reservoir, a conduitdepending therefrom, a chamber below the reservoir in communication atits lower end with said conduit, a piston adjustable in said chamber tovary the capacity of the latter, a bulb on said piston above saidchamber, a hollow rod extending from the piston to permit passage ofmaterial from the chamber through the piston into said bulb, said hollowrod being disposed within said bulb so as to form a trap, and a tubeextending from said bulb and communicating with said reservoir above theconduit.

3. A structure of the class described comprising a reservoir, a conduitdepending from the reservoir, a pair of chambers in communication attheir bases with said tube, a piston adjustable in each of said chambersto vary the capacity thereof, a bulb on each of said pistons above saidchambers, each of said pistons being hollow and having a tubular portionextending into its corresponding bulb so as to form a trap therein andto establish overflow communication between each of said chambers andits corresponding bulb, tubes establishing communication between each ofsaid bulbs and said reservoir above the conduit. and a Y stopcock meansbetween the conduit and said chambers adapted to enable one chamher tobe filled while the other chamber is emptied.

WENDAL D. LONG.

